Attempt at getting Gdk events to get finalized and freed on the UI th…

[Therzok]

…read

Possible fix for VSTS #739030 - Visual Studio Community 7.7 for Mac - crahses when holding down cursor key

[alanmcgovern]

static readonly ?

[alanmcgovern]

zero out Handle to prevent crashes due to double free?

[alanmcgovern]

One double-Dispose bug!

[Therzok]

static readonly here too

[Therzok]

Updated with PR feedback.

[slluis]

@alanmcgovern can you review?

[bratsche]

I don't know how to test this, but 👍 lgtm.

[Therzok]

using System;
using System.IO;
using Gdk;
using Gtk;

public partial class MainWindow : Gtk.Window
{
    public MainWindow() : base(Gtk.WindowType.Toplevel)
    {
        Build();
    }

	protected override bool OnExposeEvent(EventExpose evnt)
	{
		for (int i = 0; i < 1000000; ++i)
		{
			var ev = Gtk.Application.CurrentEvent;
			var copy = new Gdk.Event(ev.Handle, true);
		}

		System.GC.Collect();
		System.GC.Collect();
		System.GC.Collect();
		System.GC.WaitForPendingFinalizers();

		return base.OnExposeEvent(evnt);
	}
}

    public class MainClass
    {
        public static void Main(string[] args)
        {
            Application.Init();

			var mw = new MainWindow();
			mw.ShowAll();

			Application.Run();

		}
    }

[Therzok]

Actually, this doesn't fix the issue...

The event goes out of scope and it gets freed by native gtk. I think our only solution is to make it a ref struct and avoid the value from escaping, otherwise it'll just free invalid memory.

[Therzok]

I thought it was an UI thread bug, but it can still happen.

[Therzok]

EventOwnerChange as it's not read-only, the rest of the events could be solved by just making a copy of the GdkEvent.

[Therzok]

Closing. The problem with Gdk.Event is how it's bound and it requires breaking API to fix. We worked around it in VSMac by manually pinvoking